1. Field of the Invention
The present invention relates to an apparatus for incinerating waste materials such as waste tires, for example.
2. Description of the Prior Art
One known apparatus for incinerating waste materials such as waste tires is disclosed in Japanese Laid-Open Patent Publication No. 2-135280. Specifically, the disclosed incinerating apparatus comprises an apparatus for incinerating a waste material by processing the waste material through dry distillation and gasification.
The disclosed incinerating apparatus has a gasification furnace in which a waste material is placed. In the gasification furnace, a portion of the waste material is burned while the remainder of the waste material is subjected to dry distillation (i.e., thermally decomposed) with the heat of combustion, until finally the waste material is fully burned and ashed. A combustible gas produced when the waste material is thermally decomposed is introduced from a gasification furnace through a gas passage into a combustion furnace. In the combustion furnace, the supplied combustible gas is mixed with oxygen (air) and burned.
In order to maintain the temperature of the combustible gas as it is burned in the combustion furnace at a substantially constant level for sufficiently reducing any nitrogen oxides, the combustion furnace is supplied with an amount of oxygen that is required to combust a portion of the waste material, depending on the temperature of combustion, for thereby controlling the partial combustion of the waste material to keep substantially constant the amount of combustible gas generated in the gasification furnace and also the amount of the combustible gas introduced into the combustion furnace.
More specifically, heretofore, the combustible gas and oxygen are mixed and the mixture is combusted in the combustion furnace as follows:
The combustion furnace comprises a burner connected to the gas passage and a combustion chamber coupled to the burner. The burner and the combustion chamber have their inner walls made of a refractory material. The combustion furnace is surrounded by an air chamber connected to an oxygen supply, i.e., an air supply, and communicating with the combustion furnace through a plurality of air inlet holes defined in the inner wall of the combustion furnace. The burner is equipped with an igniter, and air is drawn from the combustion chamber by a suction fan or the like to introduce the combustion gas from the gasification furnace.
When the waste material starts being thermally decomposed in the gasification furnace, a combustible gas generated by dry distillation is introduced through the gas passage into the burner of the combustion chamber. At the same time, oxygen (air) is also introduced from the oxygen supply through the air chamber and the air inlet holes into the burner, where the oxygen is mixed with the combustion gas. The mixture is ignited by the igniter, and the combustible gas is combusted. As the dry distillation of the waste material progresses stably in the gasification furnace, the temperature of the combustible gas as it is burned in the combustion furnace is kept at a substantially constant level. The combustible gas is now combusted of its own, and the igniter is inactivated.
Since the oxygen is supplied from the air chamber through the air inlet holes into the combustion chamber to combust the combustible gas in the combustion chamber, the conventional incinerating apparatus has suffered the following drawbacks:
Inasmuch as the amount of oxygen needed to combust the combustible gas is supplied through the air inlet holes into the burner, it takes a certain period of time for the combustible gas and the oxygen to be uniformly mixed with each other. For complete combustion of the combustible gas introduced into the combustion furnace, therefore, the combustion furnace requires a retentive region for uniformizing the mixture of the combustible gas and the oxygen, and is hence relatively large in size. If the amount of combustible gas to be introduced into the combustion chamber is increased for higher combustion capability, then the period of time required for the combustible gas and the oxygen to be uniformly mixed with each other is also increased, and hence the retentive region is also increased in size, resulting in an increase in the size of the combustion chamber.
With a combustion chamber having increased size as described above for greater combustion capability, it is difficult to keep the region for uniformly mixing the combustion gas and the oxygen at a constant position in the combustion chamber. Therefore, the position where the combustion gas is burned in the combustion chamber tends to fluctuate. As the position where the combustion gas is burned fluctuates, a positive pressure may be applied to an inlet port through which the combustible gas is introduced into the combustion chamber, possibly causing the combustible gas introduced into the combustion chamber to become unstable in amount. As a consequence, it is difficult to burn the combustible gas stably at a predetermined temperature.
As the size and hence volume of the combustion chamber increase, the capacity of the suction fan for drawing air from the combustion chamber has to be increased. Furthermore, the capacity of the suction fan must be large enough to prevent a positive pressure from being imposed on the inlet port for introducing the combustible gas into the combustion chamber. Accordingly, the load exerted by the suction fan is considerably large.
Therefore, the combustion chamber of conventional incinerating apparatus is large in size, and its combustion capability cannot be greatly increased.